In conventional designs of contact lenses which are tinted, and which are used for protecting the eye or for cosmetic purposes, the tinting is achieved by use of dyes and/or pigments within the body of the contact lens, or placed upon the surface of the lens to, change or enhance the colour of the iris of the eye. Also it has recently been suggested that the colour of the iris of the eye can be masked and the apparent colour of the iris changed by using a combination of dye and/or pigment and a reflective opaque material, such as titanium dioxide.
The drawback with both of these conventional designs of contact lens is that although they change the apparent colour of the iris, the (apparent) colour they give to the iris is quite clearly false as the contact lens so manufactured do not cater for the variegated pattern and structure that is present within the true iris.
In an attempt to rectify this drawback Julius Knapp in his U.S. Pat. Nos. 4,720,188, 4,704,017 and 4,582,402 is suggesting that only a portion of the natural iris is masked by the lens so that the iris pattern is clearly visible through the tinted portion of the lens. His belief is that in this way a tinted lens can be provided with a natural variegated iris pattern which gives the tinted contact lens a more natural appearance in the eye. In order to exemplify this he suggests the use of a dot matrix approach to tinting the required portion of the contact lens. In this particular case over the portion of the lens which is to cover the iris of the eye the lens has applied to the surface thereof a dot matrix pattern which does not totally cover the portion so that a significant part of the lens in this portion allows light to be transmitted therethrough so enabling visualisation of the variagated structure of the iris.
The drawbacks with this are that the contact lens again appears false, and because of the spacing in the dot matrix pattern which allows the structure of the iris to show through. In some circumstances an the appearance of coloured islands floating on the surface of the cornea is given.
Additionally the tinting onto the finished lens surface renders the patterned lens more susceptible to problems such as deposit formation, poor comfort, loss of pattern on cleaning and wearing etc.
Also in European Patent Application No. 357062 there is disclosed a method of manufacturing coloured contact lenses in which the corresponding iris design is incorporated within the body of the lens in its finished state.